A man rows downstream at 20 km/hr and rows upstream at 15 km/hr. At what speed he can row in still water?
Answer & explanation
Correct answer: option 4
Let,
Speed of boat in still water= x
Speed of stream/current = y
According to the question:
Upstream speed (Us) = 15 km/h i.e. x - y = 15 km/h ........(i)
Downstream speed (Ds) = 20 km/h i.e. x + y = 20 km/h ........(ii)
Speed he can row in still water = x
Adding (i) & (ii):
x - y + x + y = 15 +20
2x = 35
x = 17.5 km/hr